1. Field of the Invention
This invention relates to measuring systems and more particularly to measuring systems employing six-port measuring circuits.
2. Description of the Prior Art
The so-called "six-port" approach to the measurement of microwave parameters, such as power and complex impedance, provides an attractive alternative to existing automated measurement schemes, because the requirement for frequency conversion is eliminated. Typical prior art disclosures of the six-port approach are found in a number of references, including:
G. f. engen and C. A. Hoer, "Application of an Arbitrary 6-Port Junction to Power Measurement Problems," IEEE Trans. Instrum. Meas., Vol. IM-21, pp. 470-474, Nov. 1972; PA1 C. a. hoer and G. F. Engen, "Analysis of a Six-Port Junction for Measuring v, i, a, b, z, .GAMMA. , and Phase," presented at the Proc. IMEKO Symp. Acquisition and Processing of Measurement Data for Automation, Dresden, Germany, June 17-23, 1973; PA1 G. f. engen, "Calibration of an Arbitrary Six-Port Junction for Measurement of Active and Passive Circuit Parameters," IEEE Trans. Instrum. Meas., Vol. IM-22, pp. 295-299, December 1973; PA1 C. a. hoer, "Using Six-Port and Eight-Port Junctions to Measure Active and Passive Circuit Parameters," Nat. Bur. Stand. (U.S.), Tech. Note 673, 23 pages, September 1975; PA1 C. a. hoer and K. C. Roe, "Using an Arbitrary Six-Port Junction to Measure Complex Voltage Ratios," IEEE Trans. Microwave Theory & Techniques, Vol. MTT-23, No. 12, pp. 978-984, December 1975; PA1 E. l. komarek, "An Automated Broadband System for Measurement of One-Port Microwave Parameters," Conference on Precision Electromagnetic Measurements, June 1976, Boulder, Colo., CPEM Digest, pp. 167-170; PA1 G. f. engen, "Determination of Microwave Phase and Amplitude from Power Measurements," IEEE Trans. Instrum. Meas., Vol. IM-25, No. 4, pp. 414-418, December 1976; and PA1 S. b. cohn and N. P. Weinhouse, "An Automatic Microwave Phase Measurement System," The Microwave Journal, pp. 49-56, February 1964.
Moreover, preliminary results, in the case of power at least, suggest that the requirement for a phase-locked source is eliminated as well as disclosed in the Komarek reference.
As noted (or stressed) in these prior art disclosures, the theory which has been developed applies to a five-or six-port junction of arbitrary parameters. In its present form, however, the theory provides only a limited amount of insight into the question of choosing the design goals for the five-or six-port so as to best exploit the technique. In some of the prior work, the six-port was considered an extension of the reflectometer concept. This led to six-port designs which are now considered obsolete. In other cases, guidelines, which were inferred from an incomplete analysis, have been proven to be partially in error.